Arm chair



FIG. 1 is a perspective view of the arm chair showing my new design;

FIG. 2 is a front view thereof;

FIG. 3 is a left side view thereof;

FIG. 4 is a right side view thereof;

FIG. 5 is a rear view thereof; and,

FIG. 6 is a top view thereof.

The broken lines are for environmental purposes only and form no part of the claimed design. 

The ornamental design for an arm chair, as shown and described. 